Puck lifting in Cafelat Robot?

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#1: Post by mixespresso »


I am experiencing this. For the same grind,
- If I do a quick ramp up to 6 bar with no preinfusion and I stay there, I get a good 25s shot
- Instead, if I do a 1-2ish bar preinfusion, I get a quick watery 15s shot that barely reaches 4bars at any time (the total time includes preinfusion)

The Real Sprometheus, describes exactly the same phenomenon when he reviewed the Robot on his YouTube channel. He said that the Robot suffers from puck lifting, by creating some sort of vacuum when ramping up slowly that lifts the puck and allows the water to rush below.

He describes it in this video at t=2:20

I am confused because preinfusion is pretty common in the Robot. Has anybody else experienced this?


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#2: Post by Jeff »


Remember that self-marketers often choose to portray themselves as experts that are never wrong.

Soak will soften a puck. At the same grind, I'd expect faster flow after a soak.
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#3: Post by Jonk »

He was not wrong that a coarser grind can be beneficial, but the 'puck lift' concept is nonsense. If you want to pre-infuse you need to tighten up the grind to get the same resistance, that's all.
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mixespresso (original poster)

#4: Post by mixespresso (original poster) »

I get it! Thanks!


#5: Post by Jonk »

Something real to be conscious about is that the puck will decompress when pressure is released or lowered, as seen in this video 3 minutes in:
(if I lower the pressure I prefer to do it carefully)

Like it says in the manual, you shouldn't release the pressure completely before the shot is complete or it can really mess with the puck. See the end of this other video:


#6: Post by nameisjoey »

I've never experienced this at all. If you do pre-infusion then you obviously will need to tighten the grind to achieve the same ratios.

Sprometheus has some really sus takes on stuff. This being one of them. Also doing a taste test between a spouted and bottomless portafilter is another :roll:

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#7: Post by Paul_Pratt »

I really should pay more attention to reviews :shock:

I do have a transparent portafilter for the Robot, let me dig it out.

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#8: Post by mborkow »

Why would anyone take advice from Sprometheus?

mixespresso (original poster)

#9: Post by mixespresso (original poster) »

I understand that you need to grind finer if you want to pre-infuse the puck and maintain the same flow rate.

My surprise was/is how much I had to adjust the grinder to achieve that, as the difference in the flow rate between using pre-infusion and not for the same grind was remarkable

I guess I just need to keep learning the effect of all the variables. Thanks!

mixespresso (original poster)

#10: Post by mixespresso (original poster) »

Paul_Pratt wrote:I really should pay more attention to reviews :shock:

I do have a transparent portafilter for the Robot, let me dig it out.
That would be amazing to see!